1. Field of the Invention
The present invention relates to processes for the continuous production of iron-carbon alloys in the field of the pyrometallurgy of ferrous metals.
2. Description of the Prior Art
Processes for converting iron ore to steel in batch operations are well known. The iron ore is first reduced to pig iron, in a blast furnace, which is then fed, along with scrap iron or steel, to a basic oxygen furnace or an electric furnace in a batch operation. Historically, these processes have used large amounts of energy. They have also been associated with environmental problems resulting from emissions from the processing facilities. Efforts to reduce production costs have been directed toward both of these problems. First, the reduction of expenditures associated with energy consumption and second, the reduction of expenditures as a result of improvements in the handling or minimization of environmental contaminants.
Stephens (U.S. Pat. No. RE 32,247) discloses a process for the production of iron carbide from iron ore utilizing a fluid bed process which eliminates the need for a blast furnace. The iron carbide product is then fed into either a basic oxygen furnace or an electric furnace in a batch process. However, there is no teaching of the use of the iron carbide as a feed for a continuous process to produce iron-carbon alloys.
The prior art batch processes utilizing either the basic oxygen furnace or the electric furnace are open to the atmosphere. The need for capturing and treating the gases and other emissions which are emitted from these open air processes have necessitated the installation of advanced emission control equipment. This equipment must be sized not only to treat emissions coming from the batch processes themselves, but also large volumes of air which are drawn into the equipment from the surrounding environment. This greatly increases the capital costs required to build and support batch processing steel-making facilities.
Queneau et al. (U.S. Pat. No. 4,085,923) disclose an apparatus for continuously processing non-ferrous metal ores containing significant amounts of sulfur in an enclosed reactor. This system addresses the need to contain environmentally hazardous reaction product off-gases such as sulfur dioxide and the like. Queneau et al. suggest that this system could be used for the direct production of steel from iron oxide ores. However, it is believed that the need to add large quantities of carbon fuel to the reactor in order to fully reduce the iron oxides has limited the interest in the development and use of such a process. It is further believed that the Queneau-Schuhmann (Q-S) reactor disclosed by Queneau et al. has never been successfully used for such a reaction. This is because of the apparent difficulty of adding enough heat into such a continuous reactor to complete the iron oxide reduction process. Furthermore, if coal is used as a carbon fuel to generate heat, the coal would be likely to introduce sulfur into the system, which would then necessitate the use of the costly emission control equipment previously mentioned and introduce sulfur into the metallic product.
Accordingly, a need exists for a continuous iron-carbon alloy manufacturing process utilizing an enclosed reactor. The present invention addresses this need as well as other problems associated with the production of iron-carbon alloys. The present invention also offers further advantages over the prior art, and solves other problems associated therewith.